1. Field of the Invention
The invention relates generally to the art of gas separation, that is to say, the filtering of a gaseous fluid. In a more particular sense the invention relates to filtering means falling within this general category, having a generally annular configuration in which gasketed retaining means are utilized for edge support of non-planar, sheet-like filter elements, especially those of zig-zag or pleated configurations.
2. Description of the Prior Art
In the prior art, efforts have been primarily directed, so far as replaceable filter elements are concerned, to the provision of replaceable cartridges, in which the replacement part includes more than the filter medium or element itself, and may include both the top and bottom support ring, and the inner and outer screens. This is shown, for example, in U.S. Pat. Nos. 2,979,159; 2,732,031; 3,218,785; and 3,167,416.
It would be very desirable, of course, to permit replacement of a filter element at an absolute minimum of expense, without the necessity of discarding any of the retaining or housing means incorporated in the overall filter structure for the purpose of retaining or positioning the filter element. The patents noted above have been directed toward replacing the filter medium along with cooperating retaining parts, and this is considered undesirable. The prior art has been silent, so far as is known, on the concept of retaining all components of the air filter structure considered as a whole, with the exception of the filter element itself. The prior art has failed to suggest a swift and easily practiced mode of providing access to the filter medium without the use of special tools, and permitting replacement of that medium, also without the use of special tools, with maximum ease and speed.
The prior art has further been silent on the provision of a replaceable filter element which, from the point at which it leaves the manufacturer to the time at which it is to be placed in use, may be retained as a compact, small, easily packaged product, in which the filter element comprises an inexpensive strip of paper, folded upon itself to provide a plurality of accordion pleats, and adapted to be compressed or folded flat into a small, highly compact condition while awaiting use.